Results: CML and CEL were separated with baseline resolution with a total analysis time of 21 min. The lower limit of quantification was 0.02 mol/L for both compounds. Mean recoveries from plasma samples to which CML and CEL had been added were 92% for CML and 98% for CEL. Within-day CVs were <7.2% for CML and <8.2% for CEL, and between-day CVs were <8.5% for CML and <9.0% for CEL. In healthy individuals (n ‫؍‬ 10), mean (SD) plasma concentrations of CML and CEL were 2.80 (0.40) mol/L (range, 2.1-3.4 mol/L) and 0.82 (0.21) mol/L (range, 0.5-1.2 mol/L), respectively. In hemodialysis (n ‫؍‬ 17) and peritoneal dialysis (n ‫؍‬ 9) patients, plasma concentrations of CML and CEL were increased two-to threefold compared with controls, with-

This LC-ESI-MS/MS method is easy to perform and offers reproducibility, selectivity and sensitivity for studying DNA methylation. The method allows a sample throughput of approximately 200 samples/week. The MTHFR C677T genotype influences age-related changes in DNA methylation.

Plasma levels of CML and CEL rise with deterioration of GFR. Furthermore, CML and CEL levels are associated with markers of endothelial activation independently of renal function. This suggests an involvement of these AGEs in the acceleration of cardiovascular complications in patients with renal impairment.

Studies were carried out to examine the mechanism of action of estrogen on intestinal calcium absorption in the rat. Three-month-old Wistar rats were sham-operated or ovariectomized (OVX). They were fed a diet containing 0.4% Ca, 0.4% P, and 2000 IU vitamin D3/kg. Eight weeks after operation, both OVX and sham-operated rats were randomly assigned to eight treatment groups. Five groups received per 100 g of body weight 12.5 ng calcitriol (1, 25-dihydroxyvitamin D3); 7.5 microg of estradiol-benzoate; 7.5 microg of estradiol-benzoate and 0.1 mg of ICI 182780; 12.5 ng of calcitriol and 0.1 mg of ICI 182780; and 0.1 mg of ICI 182780, respectively. Three groups received the various vehicles used. Intestinal calcium absorption was measured in vivo using single pass perfusion of the duodenum. OVX did not change intestinal calcium absorption. A pharmacological dose of estradiol-benzoate caused a significant increase in intestinal absorption of calcium, which was comparable to that of a pharmacological dose of calcitriol in both OVX and sham-operated rats. Estrogen-induced rise in intestinal calcium absorption was completely blocked to basal level by the pure estrogen receptor (ER) antagonist ICI 182780. In contrast, ICI 182780 did not antagonize calcitriol-enhanced intestinal calcium absorption. Our findings suggest that estrogen stimulates intestinal calcium absorption via an ER.

OBJECTIVE -We studied acute changes in markers of glycoxidative and lipoxidative stress, including oxidized LDL, N ε -(carboxyethyl)-lysine (CEL), N ε -(carboxymethyl)-lysine (CML), and 3-deoxyglucosone (3DG), following two consecutive meals. RESEARCH DESIGN AND METHODS -Postmenopausal women (27 with normal glucose metabolism [NGM], 26 with type 2 diabetes) received two consecutive fat-rich meals and two consecutive carbohydrate-rich meals on two occasions. Glucose and triglyceride concentrations were measured at baseline and 1, 2, 4, 6, and 8 h following breakfast; lunch was given at 4 h. Oxidized LDL-to-LDL cholesterol ratio, CEL, CML, and 3DG were measured at baseline and at 8 h.RESULTS -Fasting oxidized LDL-to-LDL cholesterol ratio, 3DG, and CML were higher in women with type 2 diabetes compared with women with NGM and were comparable to the postprandial values at 8 h in NGM. Postprandial rises in the oxidized LDL-to-LDL cholesterol ratio and 3DG were similar in both groups. However, the oxidized LDL-to-LDL cholesterol ratio increased more after the fat-rich meals, whereas CML and 3DG increased more after the carbohydrate-rich meals. After the fat-rich meals, the increase in the oxidized LDL-to-LDL cholesterol ratio correlated with postprandial triglycerides, whereas the increase in 3DG was correlated with postprandial glucose.CONCLUSIONS -The acute changes in markers of glycoxidative and lipoxidative stress in both type 2 diabetes and NGM suggest that postabsorptive oxidative stress may partly underlie the association of postprandial derangements and cardiovascular risk. Diabetes Care 30:1789-1794, 2007P atients with type 2 diabetes have an increased risk of cardiovascular disease (CVD) (1), which can only partly be explained by classical CVD risk factors such as hypertension, high LDL cholesterol, low HDL cholesterol, and smoking (2). In postmenopausal women compared with men, the relative risk of CVD conferred by type 2 diabetes is even higher (3). Zilversmit (4) postulated in 1979 that disturbances in postprandial metabolism may contribute to the excess risk of CVD due to postprandial elevations of glucose and triglyceride-enriched lipoproteins (5,6).Oxidative stress is regarded as a common pathway by which many of the classical CVD risk factors and postprandial dysmetabolism may initiate and promote atherosclerosis (7). Indeed, elevated levels of oxidized LDL are associated with an increased risk for CVD (8). Prolonged exposure to a high-fat diet has been shown to result in an increase in plasma levels of oxidized LDL (9). Another mechanism that might link postprandial dysmetabolism and the risk of CVD in patients with type 2 diabetes includes the formation of advanced glycation end products (AGEs), which are related to micro-and macrovascular complications (10). Two of the most studied AGEs, N ε -(carboxyethyl)lysine (CEL) and N ε -(carboxymethyl)lysine (CML), can be formed on proteins by both glycoxidation and lipid peroxidation pathways. ␣-Dicarbonyl compounds such as 3-deoxyglucosone (3DG), glyoxal,...

1 The absorption kinetics of orally administered strontium chloride and its reproducibility were investigated in healthy volunteers after administering strontium either under fasting conditions (study I, n=8) or in combination with a standardized meal (study II, n=8). Each subject received strontium orally at day 0, 14, and 28 and intravenously at day 42. The study was performed as part of a project in which a simple clinical test for measuring intestinal calcium absorption is being developed, based on the use of stable strontium as a marker. 2 Plasma strontium concentration-time curves were analysed by noncompartment analysis and a four compartment disposition model. Within a volunteer each oral curve was fitted simultaneously with the intravenous curve, by which means a two segment model for absorption was revealed. 3 Mean absolute bioavailability of strontium was 25% without a meal and 19% with a meal, whereas the intraindividual variation was 24% and 20%, respectively. 4 Various limited sampling absorption parameters were determined in order to select a potential test parameter for measuring intestinal calcium absorption using strontium as a marker. Fractional absorption at 4 h (Fc 240 ), obtained after co-ingestion of strontium with a meal, appeared to be the best test parameter, because it represented bioavailability well (r=0.90 ).

Objective: Metformin has been reported to reduce a-dicarbonyls, which are known to contribute to diabetic complications. It is unclear whether this is due to direct quenching of a-dicarbonyls or to an improvement in glycemic control. We therefore compared the effects of metformin versus repaglinide, an antihyperglycemic agent with an insulin-secreting mechanism, on the levels of the a-dicarbonyl 3-deoxyglucosone (3DG). Methods: We conducted a single-center, double-masked, double-dummy, crossover study involving 96 nonobese patients with type 2 diabetes. After a 1-month run-in on diet-only treatment, patients were randomized to either repaglinide (6 mg daily) followed by metformin (2 g daily) or vice versa each during 4 months with a 1-month washout between interventions. Results: 3DG levels decreased after both metformin (K19.3% (95% confidence interval (CI): K23.5, K14.8)) and repaglinide (K20.8% (95% CI: K24.9, K16.3)) treatments, but no difference was found between treatments (1.8% (95% CI: K3.8, 7.8)). Regardless of the treatment, changes in glycemic variables were associated with changes in 3DG. Specifically, 3DG decreased by 22.7% (95% CI: 19.0, 26.5) per S.D. decrease in fasting plasma glucose (PG), by 20.0% (95% CI: 16.2, 23.9) per S.D. decrease in seven-point mean plasma glucose, by 22.5% (95% CI: 18.6, 26.6) per S.D. decrease in area under the curve for PG, by 17.2% (95% CI: 13.8, 20.6) per S.D. decrease in HbAlc, and by 10.9% (95% CI: 6.4, 15.5) per S.D. decrease in Amadori albumin. In addition, decreases in 3DG were associated with decreases in advanced glycation endproducts and endothelial markers. Conclusion: Improved glycemic control induced by both metformin and repaglinide is associated with a reduction in 3DG levels in nonobese individuals with type 2 diabetes. This may constitute a shared metabolic pathway through which both treatments have a beneficial impact on the cardiovascular risk.

Methionine, an essential amino acid required for protein synthesis, is the only parameter that dramatically decreases with gestational age. The AdoMet/AdoHcy ratio exponentially increases from 25 weeks of gestation, which could reflect increasing methylation capacities. The negative correlation between betaine and total Hcy together with a constant betaine to dimethylglycine ratio during gestation suggests that betaine may be used as a methyl donor during fetal life.